Numerous devices have been used to position tissue at a surgical site to aid in the performing of surgical procedures. Retractors, for example, have been used to hold an artery in position during operations adjacent to the heart to prevent movement of the artery. This serves to minimize the risk of injury to the artery and adjacent tissue and can facilitate the desired anastomosis.
A recently developed procedure, referred to as the minimally invasive direct coronary artery bypass procedure, has been used to graft onto a coronary artery without cardiopulmonary bypass. This procedure involves the grafting of the left internal mammary artery (LIMA) onto the left anterior descending (LAD) or other artery. As this procedure does not require the use of a heart lung machine to oxygenate and pump blood, the morbidity and mortality associated with this procedure is substantially lower than previous bypass techniques. A problem associated with the minimally invasive procedure, however, is that while the heart continues to pump during the procedure, the motion of the heart can interfere with the surgeon""s task of attaching the LIMA to the LAD. There is also a need to stop blood flow in the area of the graft to maintain a clear field of view and provide precise suture placement.
Two basic strategies have been employed to address the problem of operating on a moving site, one being the use of pharmacological agents to limit heart motion, and the other being mechanical, such as a two prong retractor that is pushed down against the heart on both sides of the artery, or alternatively, upward traction away from the moving heart by traction tape or suture thread. Both of these options, however, have problems associated with them. Both options are susceptible to some movement of the vessel grafting site. The use of pharmacological agents is undesirable and impairs circulatory function. Traction by compression of the heart against the spine does serve to immobilize the site but can compromise the ability of the heart to maintain circulation and result in hypotension. Upward traction can involve circumferential compression of the artery to occlude the artery and prevent blood flow, however upward traction that is sufficient to immobilize the site can cause injury, stenosis or occlusion of the vessel.
There is a continuing need however for improvement in devices and methods for retaining tissue at surgical sites to further reduce the risks associated with surgical procedures where the devices and methods are inexpensive, safe and reliable.
The present invention relates to a surgical retractor for immobilizing tissue at a surgical site and to a method of using the retractor during a surgical procedure. A preferred embodiment of the retractor includes a retaining element having an aperture that exposes the surgical site and a holder that is used to position tissue at the surgical site relative to the retaining element. A handle can be attached to or fabricated with the retaining element or platform so that the user can manipulate the position of the retractor as needed.
In a preferred embodiment of the invention a connector such as elastic tape or thread is used to position tissue at the surgical site within the retractor aperture and to prevent movement of the tissue during the procedure. The connecting cord, thread or tape also aids in the compression of the artery in a grafting procedure to occlude flow on one or both sides of the surgical site. The cord is attached to the holder on the retaining element. A preferred embodiment of the holder can be a plurality of slits or openings positioned on both sides of the retractor that receive and frictionally secure the cord on both sides of the aperture. In another preferred embodiment a mechanical fastener is used to grip both sides of the cord. The fastener can be a spring mounted valve, for example, that allows the user to adjust the tension in the cord.
A preferred embodiment of the invention comprises a retaining element or base having two sections that can be separated after the procedure is complete to permit removal of the retractor from under the grafted artery. Another preferred embodiment uses a side opening in the platform of the retractor that extends to the aperture so that the grafted artery slips through the side opening during removal. During minimally invasive direct coronary artery bypass operations, one or more surface sections of the retractor platform can be positioned against the inner surface or posterior aspect of one or both ribs adjacent to the surgical site. Thus, the size and geometry of the platform are selected to utilize the adjoining ribs where the upper surface of the platform frictionally engages the inner surface of one or more ribs to hold the retractor in a fixed position. The retractor can be beneficial in any procedure where it is necessary to stabilize a surgical site. For example, the retractor can also be used for grafting onto the diagonal, right or other coronary arteries without altering the heart""s pumping function.
The coronary arteries are about 1-2 mm in diameter, and the pumping heart can move these arteries over distances of several millimeters during each heartbeat. As the movement of even 1 or 2 millimeters can result in a displacement of the grafting site that can substantially interfere with effective anastomosis, it is desirable to restrain movement of the artery at the surgical site in any direction to less than 1 mm. The retractor of the present invention restrains movement in the plane of the base to less than 0.5 mm, and preferably less than 0.2 mm.
In a preferred embodiment of the invention, the handle or articulating arm that is secured to the platform can be held in position by the user, attached to a frame that is fixed around the operative site or simply clipped to a drape around the site.
In a preferred embodiment of the invention, the surgical retractor can be optically transmissive or transparent to allow enhanced visibility of the underlying adjacent tissue at the desired surgical site. The aperture of the retractor in accordance with the present invention, varies in size and can range from 1-3 cm in length and 5-15 mm in width.
In a preferred embodiment, the surgical retractor has raised holder elements disposed in the longitudinal dimension of the retractor, each holder element having a pair of slots that frictionally grip an end of a connector such as an elastic tape or thread which extends through the aperture to attach tissue to the retractor. The surgical retractor further has run off areas on the four coners of the retractor that have a downward slope. These run off areas allow for fluid drainage during the surgical procedure to assist in maintaining the surgical field adjacent to the aperture clear of blood during the anastomosis. The four coners of the base have a gradually thinner cross-section to provide the downward slope.
In a preferred embodiment, the surgical retractor includes a two-component configuration to allow the retractor to be separated after the surgical procedure is completed to permit removal of the retractor from under the grafted artery. A pair of plastic tabs extend between the two components to securely retain the components together during the procedure and to allow the surgeon to release the components following the procedure by cutting the tabs with a knife.
In another preferred embodiment, the surgical retractor has slots or grooves on the bottom surface of the retractor to allow the user to place the connector such as elastic tape or thread, either under or over the retractor to position tissue at the surgical site within the retractor aperture and to prevent movement of the tissue during the procedure. When these slots are used the tapes are threaded through the tissue of the heart-wall of the patient and then aligned to be positioned in the desired underlying slots. The surgeon can include additional tissue around the blood vessel as the tapes are tightened so that the blood vessel is compressed by the adjacent tissue rather than being constricted by the tapes. Additionally, the surgeon can position the tapes at a relatively sharp angle of approach. Alternately, a wider angle of approach may be used wherein the tapes are threaded around the outer surface of the retractor so that more tissue is positioned between the tapes and the blood vessel. The route used by the surgeon varies depending on the depth of the desired blood vessel and the surgeon""s preferred approach to performing the anastomosis.
In a preferred embodiment, portions of the bottom surface form a slightly curved surface which extends a slight distance downwardly parallel to the lengthwise dimension of the aperture which assists in retaining the retractor in the desired position on the heart wall of the patient as it continues beating. The bottom surface that surrounds the artery and is in contact with the pericardium can be roughened or abraded to frictionally engage the pericardium around the artery and thereby locally restrict heart motion around the surgical site. There are elevated regions or protrusions such as ridges or nubs, for example, disposed on the bottom surface of the retractor to frictionally engage the pericardium wall around the surgical site.
When used in a minimally invasive coronary bypass procedure, the retractor is positioned to expose the left anterior descending (LAD) artery grafting site after incision, removal of the rib section and dissection of the left internal mammary artery (LIMA) from the chest wall. A pair of cords, for example, silastic tape (i.e. a silicon elastomer) or suture thread, are passed through the myocardium at two locations flanking the artery grafting site with blunt needles. The four ends of the two cords are connected to the platform holder with sufficient tension to occlude blood flow on both sides of the operative site. The tapes compress the artery against the bottom surface of the platform while they hold the artery grafting site in a fixed position relative to the aperture. The coronary artery is opened longitudinally and the end of the mammary artery is sewn to the graft opening with multiple fine sutures. The cords are released, blood flow is restored and the anastomosis is inspected for hemostatis and other defects and the wound is closed.
The platform can include tabs or cord retainers that extend into the aperture to provide a surface against which the arteries can be compressed.